script_1.py - Basic List Operations - CRUD

Code

#!/usr/bin/env python3
"""Basic List Operations - CRUD

Summary: Demonstrates Create, Read, Update, Delete operations on lists.
Use when: You need to manage a collection of items that can change over time.
Common in: Shopping carts, todo lists, user management systems.
"""

# CREATE - Initialize a list
tasks = ["Write code", "Test code", "Deploy code"]
print("Initial tasks:", tasks)

# READ - Access elements
print(f"\nFirst task: {tasks[0]}")
print(f"Last task: {tasks[-1]}")
print(f"Total tasks: {len(tasks)}")

# UPDATE - Modify existing element
tasks[1] = "Write tests and test code"
print(f"\nUpdated tasks: {tasks}")

# DELETE - Remove element
removed = tasks.pop(0)
print(f"\nCompleted: {removed}")
print(f"Remaining: {tasks}")

# ADD - Append new element
tasks.append("Monitor production")
print(f"Added new task: {tasks}")

Explanation

Line 10: tasks = ["Write code", "Test code", "Deploy code"] - [] creates a list (mutable sequence type) - List contains string elements - tasks variable is type list - Lists are ordered (maintain insertion order)

Line 13: print(f"\nFirst task: {tasks[0]}") - [0] is index notation (bracket syntax for accessing elements) - Index 0 is first element (zero-based indexing) - Returns string type (the element at that position)

Line 14: print(f"Last task: {tasks[-1]}") - Negative index counts from end - -1 is last element, -2 is second-to-last, etc. - Alternative to tasks[len(tasks) - 1]

Line 15: print(f"Total tasks: {len(tasks)}") - len() is built-in function returning integer (number of elements)

Line 18: tasks[1] = "Write tests and test code" - Assignment to index updates element in place - Lists are mutable (can modify after creation) - Index 1 is second element - Original value is replaced (not inserted)

Line 22: removed = tasks.pop(0) - .pop() is list method that removes and returns element - Argument 0 specifies index to remove - Modifies list in place (removes element) - Returns the removed element (string type) - List length decreases by 1

Line 27: tasks.append("Monitor production") - .append() adds element to end of list - Mutates list (modifies in place) - List length increases by 1 - No return value (returns None)